Current Affairs 8th Class

Reasoning and Aptitude   Learning process is dependent on ones ability to think logically and reason quickly and effectively. So Reasoning and logic skills are an important part in our progress as these skills are very useful in our day to day lives. In this chapter, we will learn various problems related to reasoning and aptitude.   Problems Based on Blood Relations The efficiency in doing the problems of blood relations depends upon the knowledge of the blood relations. Some of the important relations are given below,   Relations of Paternal Side   Ø    Father's father  Grandfather Ø    Father's mother  Grandmother Ø    Father's brother  Uncle Ø    Father's sister  Aunt Ø    Children of uncle  Cousin Ø    Wife of uncle  Aunt Ø    Children of aunt  Cousin Ø    Husband of aunt  Uncle   Relations of Maternal Side   Ø    Mother's father  Maternal grandfather Ø    Mother's mother  Maternal grandmother Ø    Mother's brother  Maternal uncle Ø    Mother's sister  Aunt Ø    Children of maternal uncle  Cousin Ø    Wife of maternal uncle  Maternal aunt   Note:   (i) My mother's or father's son is my Brother. (ii) My mother's or father's daughter is my Sister. (iii) My mother's or father's father is my Grandfather. (iv) My mother's or father's sister is my Aunt.   ·         Example:   How is Hema's mother's mother's daughter - in law's daughter related to Hema? (a) Sister                      (b) Mother (c) Cousin                    (d) Aunt (e) None of these   Answer (c) Explanation: Hema's mother's mother  Hema's (Maternal) grandmother Hema's Grandmother's Daughter - in - law  Hema's (Maternal) Aunt Hema's Aunt's daughter  Hema's Cousin   ·         Example:   Pointing towards a lady in a photograph, a girl said, "She is the sister of my mother's husband". How is the girl related to the lady? more...

Pollution of Air and Water   Pollution Our environment is our surrounding. It comprises all living and non-living things. Any undesirable change in the physical, chemical or biological characters of air, water and soil leads to environmental pollution which is harmful to human beings directly or indirectly.   Pollutant A pollutant is a substance that may be added to the environment directly or indirectly by man or natural events, to an extent which adversely affects humans, animals, vegetation and other materials.   Air Pollution Air pollution is defined as the addition of undesirable materials into the atmosphere either due to human activities which adversely affect the quality of the air and hence life on earth or through natural process like volcanic eruptions.   Causes of Air Pollution 1. Burning of fossil fuels                       2. Motor vehicles 3. Thermal power plants                      4. Industries 5. Human activities                             6. Volcanic eruptions   Greenhouse Effect Greenhouse effect may be defined as a phenomenon that enables the earth's atmosphere to trap the heat from the sun and prevent it from escaping into the outer space, there by warming the earth's surface.   Acid Rain The burning of fossil fuels containing sulphur, nitrogen and carbon produces acidic oxides of these elements. Carbon dioxide, an oxide of carbon, dissolves in water droplets to produce carbonic acid (a weak acid). The oxides of sulphur and nitrogen react with water to form sulphuric acid  and nitric acid  respectively. These acids come down to earth with rain water.   Water Pollution Water is a natural resource. About seventy one percent surface of the earth is covered with water and is called hydrosphere. There is plenty of water on our planet, but its distribution is not uniform. About 97.4% of the total water on the earth is present in oceans. Only 0.01% of the total water on the earth, is available as freshwater, is used by us and other living beings. The water in the oceans is so salty that it cannot be used for most purposes.   Sources of Water Pollution   v    Domestic waste v    Industrial waste v    Agricultural waste   Effect of Pollution on Water Bodies   v    Oxygen Depletion v    Toxicity v    Algal bloom v    Water borne diseases

Solar System and Some Natural Phenomenon   Solar System Solar system, the sun and everything that orbits the sun, including the planets and their satellites, the dwarf plants, asteroids, kuiper belt objects and comets.   Related image Solar System   Sun Sun is the closest star to the earth. Its average distance from the earth is about 150 million kilometres. It consists mainly of hydrogen and helium. Diameter of sun is about 1.4 million km. The temperature at its surface is about.   Planets Based on the distances of planets from the sun they are as follows: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. All the planets revolve around the sun in a fixed path called orbit. Planets which are close to the sun like Mercury, Venus, Earth and Mars are called inner planets or terrestrial planets. Jupiter, Saturn, Uranus and Neptune are known as the outer planets or jovian planets as they are far from the sun.   Mercury - is nearest to the sun. This planet has a rocky surface which is covered with craters. It is the smallest planet of the solar system.   Venus - is the second planet from the sun. Venus is a rocky planet. It is the hottest planets as its atmosphere is mainly made up of carbon dioxide. It rotates on its axis from east to west.   Earth - is the third planet from the sun. Earth's atmosphere has sufficient oxygen, the gas we need to live and water.   Mars - is also known as a red planet. The thin atmosphere of mars contains mainly carbon dioxide with small amounts of nitrogen, oxygen, noble gases and water vapour. It appears red due to the high amount of iron oxide present on its surface.   Jupiter - is the biggest planet and is made mainly of hydrogen and helium.   Saturn - is the second biggest planet of the solar system and is made up of mainly hydrogen and helium. It has well developed system of rings surrounding it. It is the least dense planet and can float in water.   Uranus - is the third biggest planet of the solar system and is mainly made up of hydrogen and helium.   Neptune - is the outermost planet of the solar system and is made mainly of liquid and frozen hydrogen and helium gases.   The Moon A celestial body that revolves around a planet is known as natural satellite or moon of the planet. The earth has only one moon. It reflects the light of the sun. Its surface is covered with craters and mountains.   Phases of moon Shapes of the bright more...

Chemical Effects of Current and Light   Chemical reactions are caused by passing of electric current through a conducting solution. This is called chemical effect of electric current.   Electric Current An electric current is a movement of charge. When two objects with different charges come in contact with each other and redistribute their charges, an electric current flows from one object to the other until the charge is distributed according to the capacities of objects. If two objects are connected by a material that lets charge flow easily, such as copper wire, then an electric current flows from one object to the other through then an Electric current is measured in ampere.   Conduction of Electric Current Through Liquids A solution of a substance or a substance in a liquid state which can conduct electricity is called an electrolyte. Most liquids that conduct electricity are solutions of acids, bases And salts. The Chemical decomposition of an electrolyte on passing an electric current through it is called electrolysis. Electrolysis is used very widely in industies like electroplating of metals, refining of copper and extraction of aluminum from ore. To make electrolysis happen there require two conductors cathode (-) and anode (+). Related image Process of Electrolysis   Electroplating The process of covering a more reactive metal with a less reactive metal with the help of electricity is known as electroplating. Material to be plated should be connected cathode while anode usually loses material.   Light The sense of sight is one of the most important senses. Through this we see things around us. Light is an electromagnetic radiation, specifically radiation of a wavelength that is visible to the human eye.   Luminous and Non-luminous Objects   v    The objects which emit their own light are called luminous objects. For example, sun, stars, electric bulb, glowing tube light, torch, etc. v    The objects which do not emit their own light are called non-luminous objects. For example, the moon, earth, table, chair, book, trees, etc.   Reflection of Light is the phenomenon of sending back light rays which fall on the surface of an object.   Laws of Reflection   According to first law of reflection: the incident ray, the reflected ray and the normal ray, all lie in the same plane.                                                   According to second law of reflection: the angle of incidence is always equal to angle of reflection.   Periscope is a long, tubular device used to observe over, around or through an object that is out of direct line of sight. A periscope works on the reflection of light from two plane mirrors arranged parallel to one more...

Force, Friction and Sound   Force A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force acting each of the objects. Force acting between objects can be placed into two categories:   Contact Forces Are those types of forces which result when the two interacting objects are perceived to be physically contacting each other.   Types of Contact Forces   v    Muscular Force - is the force exerted by the muscles of the body. This force can be applied to an object only when our body is in contact with the object, therefore muscular force is a contact force. v    Frictional Force - is the force which opposes the motion of one body over another body.   Non-contact Forces Are those forces which result when the two interacting objects are not in physical contact with each other.   Types of Non-contact Forces   v    Gravitational Force - is the force by which all things with mass are brought toward one another. It is the gravitational force between the sun and the earth which holds the earth in its orbit around the sun. v    Magnetic Force - is the force exerted by a magnet. The magnetic force between two magnets placed near one another can be that of "attraction" or "repulsion" depending upon which poles of the two magnets are facing each other. v    Electrostatic Force - is the force exerted by an electrically charged object.   Pressure Pressure, in mechanics is the force per unit area exerted by a liquid or gas on a body surface, with the force acting at right angles to the surface uniformly in all directions. Mathematically: Where P is the pressure, F is the normal force and A is the area. Unit of pressure is Pascal or.   Atmospheric Pressure The pressure exerted by the atmosphere is called atmospheric pressure. It decrease with increase in height.   Friction Friction is the force that opposes the motion of an object when the object is in contact with another object or surface. Friction results from two surfaces rubbing against each other or moving relative to one another. It can hinder the motion of an object or prevent an object from moving at all. The strength of frictional force depends on the nature of the surfaces that are in contact and the force pushing them together.   Causes of Friction Friction occurs because rough surfaces tend to more...

Reproduction and Adolescence   Reproduction Reproduction is a process by which all living organisms produce off springs. Reproduction is one of the essential functions of plants, animals and other organisms for the preservation of the species. In almost all animals, reproduction occurs during or after the period of maximum growth.   Types of Reproduction   Asexual Reproduction It is a type of reproduction by which offspring arise from a single organism and it does not involve the fusion of gametes.   Types of Asexual Reproduction   v    Binary fission - in this type of reproduction the fully grown parent cell splits into two halves, producing two new cells. For example, amoeba and paramecium. Image result for binary fission in amoeba   v    Budding - in this type of reproduction, from theparent organism a bulb-like projection called bud arises which grows and eventually break away from the parent. For example: hydra and yeast. Image result for budding in yeast Budding in yeast   v    Vegetative Propagation - is found in plants where new independent individual are formed without the production of seeds and spores. For example, propagation through leaves in Kalanchoe, Bryophyllum. Image result for vegetative propagation by leaves in bryophyllum Vegetative propagation by leaves in Bryophyllum   v    Spore Formation - is found in nonflowering plants such as fungi and bacteria. In this method, the plant produces hundreds of tiny spores which can growl into new plants. Image result for spore formation in rhizopus Spore formation in Rhizopus   v    Fragmentation - in this method a new organisms grows from a fragment of the parent. Each fragment develops into a mature, fully grown individual. For example, lichens, liverworts. Image result for fragmentation in spirogyra   Sexual Reproduction It is a method of reproduction of producing a new individual from two parents by combining their genetic information. For example, human beings, dog, cat, etc.   Fertilisation The process of formation of zygote by the fusion of male gamete and female gamete is known as fertilisation. There are two types of fertilization: internal and external Fertilisation. Image result for fertilisation in humans (fertilised egg) Fertilisation in humans from a zygote (fertilised egg)   v    Fertilization - this type of fertilization occurs outside the animals body. For example, starfish, jellyfish, etc. more...

Cell Structure and Function   Cell Structure Cells fall into one of the two categories: prokaryotic or eukaryotic. In a prokaryotic cell, found only in bacteria and archaebacteria, all the components, including the DNA, mingle freely in the cell's interior, a single compartment. Eukaryotic cells, which make up the plants, animals, fungi and all other life forms contain numerous compartments or organelles within each cell. The DNA in eukaryotic cells is enclosed in a special organelle called the nucleus, which serves as the cell's command centre and information library. The term prokaryote comes from Greek word that mean "before nucleus" or "prenucleus," while eukaryote means "true nucleus."   Prokaryotic Cells Prokaryotic cells are among the tiniest of all cells, ranging in size from 0.0001 to 0.003mm in diameter. These cells, which can be rodlike, spherical or spiral in shape are surrounded by a protective cell wall.    Image result for Prokaryotic Cells   Eukaryotic Cells Eukaryotic cells are typically about ten times larger than the prokaryotic cells. In animal cells, the plasma membrane rather than a cell wall, forms the cell's outer boundary. With a design similar to the plasma membrane of prokaryotic cells, it separates the cell from its surroundings and regulates the traffic across the membrane. Image result for animals cell diagram     The eukaryotic cell cytoplasm is similar to that of the prokaryotic cell except for one major difference. Eukaryotic cells have a nucleus and numerous other membrane-enclosed organelles. Like separate rooms of a house, these organelles enable specialized functions to be carried out efficiently. For example, the building of proteins and lipids takes in separate organelles where specialized enzymes geared for each job are located. The nucleus is the largest organelle in an animal cell. It contains numerous strands of DNA, the length of each strand being many times the diameter of the cell. Unlike the circular prokaryotic DNA, long sections of eukaryotic DNA pack into the nucleus by wrapping around proteins. As a cell begins to divide, each DNA strand folds over on to itself several times, forming a rod-shaped chromosome.   Cell Functions To stay alive, cells must be able to carry out a variety of functions. Some cells must beable to move and most cells must be able to divide. All cells must maintain the right concentration of chemicals in their cytoplasm, ingest food and use it for energy, recycle molecules, expel wastes and construct proteins. Cells must also be able to respond to changes in their environment.   Movement Many unicellular organisms swim, glide, thrash or crawl to search for food and escapes enemies. Swimming organisms often move by means of a flagellum, a long tail-like structure made of protein. For example, many bacteria have one, two or many flagella that rotate like propellers to drive the more...

Conservation of Plants and Animals   Related image   Conservation is the sustainable use and protection of natural resources including plants, animals, mineral deposits, soil, clean water, clean air and fossil fuels such as coal, petroleum and natural gas. Natural resources are grouped into two categories: renewable resource is the one that may be replaced over the time by natural processes such as fish populations, natural vegetation or is inexhaustible such as the solar energy. Nonrenewable resources are those which are limited in supply and cannot be replaced even over extremely long period of time. The nonrenewable resources include fossil fuels and mineral deposits, such as iron ore and gold ore. Conservational activities for the nonrenewable resources focus on maintaining an adequate supply of these resources well in the future. Natural resources are conserved for their biological, economical and recreational values, as well as their natural beauty and importance to the local cultures. For example, tropical rain forests are protected for their important role in both the global ecology and the economic livelihood of the local culture. A coral reef may be protected for its recreational value for scuba divers and a scenic river may be protected for its natural beauty.   Biodiversity Biodiversity or biological variety denotes the number and variety of different organisms and ecosystems in a certain area. We should conserve forests and wildlife to preserve biodiversity to prevent endangered species from becoming extinct and to maintain ecological balance in nature.   Deforestation Image result for Deforestation Deforestation means large scale removal of forest prior to its replacement by other land uses. Forests are removed for a variety of reasons, including agriculture, timber harvesting, mining and to make way for roads, dams and human settlements.   Protected Areas Protected areas are the areas of land or sea especially dedicated to the protection and maintenance of biodiversity. These are managed through legal means and have set up within the legal frame work of Indian wildlife (Protection) Act, 1972. Examples of protected areas are national parks and wildlife sanctuaries.   National Parks A national park is a large area dedicated to conserve the environment, natural resources and the wildlife therein. In a national park,   v    Private rights are non-existent. v    forestry operations, grazing of animals and hunting of animals are prohibited v    visitors are allowed to enter only for study, cultural and recreative purpose v    Exploitation of habitat or wildlife is banned.   Wildlife Sanctuaries A wildlife sanctuary is similar to a national park. However, it aims only at conservation of species. The wildlife sanctuaries have the following features:   vCoal and Petroleum   Coal   It is composed primarily of carbon and hydrogen along with small quantities of other elements, notably sulphur. It is a nonrenewable resource.   Coal Formation   Image result for Coal Formation   Coal is a sedimentary rock formed from plants that flourished millions of years ago when tropical swamps covered large areas of the world. Lush vegetation, such as early club mosses, horsetails, and enormous ferns, thrived in these swamps. Generations of this vegetation died and settled to the swamp bottom and over time the organic material with a high percentage of carbon. Layers of mud and sand accumulated over the decomposed plant matter, compressing and hardening the organic material as the sediments deepened. Over millions of years, depending sediments layers, known as overburden, exerted tremendous heat and pressure on the underlying plant matter, which eventually became coal.   Types of coal Related image   As geological process apply pressure to dead dead biotic matter over time, under suitable conditions it is transformed successively into:   Peat: It is considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland.   Lignite: It is also referred as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation.   Bituminous: It is dense rock which is usually black but sometimes dark brown, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.   Anthracite: It is the highest rank of coal; a harder, glossy, black coal used primarily for give some other use.   Petroleum It is, also known as crude oil, a fossil fuel, formed over a period of millions of years, from organisms that lived in the sea at that time. Their dead bodies sank to the bottom of sea and were covered with mud and sand. Due to high pressure, heat, in the absence of air, the dead remains of tiny plants and animals were slowly converted into petroleum. Process of separating crude petroleum oil into more useful fractions is called refining. The various useful fractions obtained by the refining of petroleum are: Petroleum gas, Petrol, Kerosene, Diesel, Lubricating oil, Paraffin wax and bitumen.   Combustion It is a process of rapid oxidation or burning of a substance in the presence of oxygen to produce heat and light. Requirements for the occurrence of combustion are:   v    Presence of combustible substance v    Presence of supporter of combustion (like air or oxygen). v    more...

Materials   Fibres A fibre is a piece of fabric that is long, thin and flexible. Plant fibres are the basis of febric such as cotton, silk and wool fibres come from animals. Many artificial fibres have also been invented such as rayon, nylon, polyester, acrylic, etc.   v    Rayon - is also known as 'artificial silk'. Cellulose which is obtained from wood pulp is the raw material to prepare rayon. It is used in home furnishings, suits, ties, blouses, sportswear, etc. v    Nylon - is entirely made of chemicals. It is very strong, elastic, light and water-resistant fiber. It is lustrous in appearance. It is used in making ropes, tents, fishing nets and parachutes. v    Polyester - is made from 'petroleum'. It is very strong, crease resistant, light, elastic and absorbs very little water. It is used in making pants, shirts, suits, jackets, etc. v    Acrylic - is made from a chemical called 'acrylonitrile'. Due to its wool like feel, acrylic fiber is often used as a substitute for wool. It is used for making sweaters, shawls, blankets, sportswear, socks, carpets, etc.   Plastics A plastic is a synthetic material which can be moulded into desired shape when it is soft and then hardened to produce a durable article. For example, polyethene, PVC, Bakelite, Melamine and Teflon.   Types of Plastics:   v    Thermoplastics - which can be moulded into different shapes again and again by heating. For example, polyethene, PVC. v    Thermosetting plastics - which cannot be moulded by heating. For example, bakelite and Melamine.   Metals Metals are defined as elements which form positive ions by losing electrons. For example, sodium, potassium etc.   Physical Properties   v    Good electrical conductors and heat conductors. v    They are malleable i.e. can be beaten into thin sheets. v    They are ductile i.e. can be stretched into wires. v    Possess metallic lustre. v    Opaque in nature. v    Solid at room temperature (except Hg).   Chemical Properties   v    Usually have 1-3 electrons in their outer shell. v    Lose their valence electrons easily. v    Form oxides that are basic. v    Are good reducing agents. v    more...



LIMITED OFFER HURRY UP! OFFER AVAILABLE ON ALL MATERIAL TILL TODAY ONLY!

You need to login to perform this action.
You will be redirected in 3 sec spinner

Free
Videos